Solar farms can mitigate negative impacts of whiplash weather on plant communities in a dryland ecosystem

Societal Impact Statement Utility‐scale solar energy (USSE) development generates novel questions regarding coupling clean energy production with terrestrial ecosystem services (e.g., forage production, pollinator support). We found that a USSE array sited in a fallowed cropland maintained a reseeded native plant community even a decade post‐restoration and that the array better supported native plant community persistence with higher quality forage during extreme drought than adjacent land. These effects were diminished following extreme rainfall; however, the array conferred greater plant community stability and productivity across a whiplash weather period, underscoring the potential to support socio‐ecologically synergistic USSE development in historically farmed drylands. Summary Uncertainty about the ecological outcomes of utility‐scale solar energy (USSE) development in fallowed cropland that incorporates plant community restoration is compounded by concurrent increases in extreme weather variability that challenge our ability to optimally guide this land use. We characterized the persistence and characteristics of a reseeded native plant community within a USSE site developed in 2014 upon fallowed farmland in the semi‐arid Carrizo Plain, California, as the system experienced a whiplash weather period of extreme drought (2021–2022) followed by extreme rainfall (2022–2023) and then more moderate rainfall (2023–2024). We studied plant community responses in under/alley paired microsites and reference areas within the array fencing but beyond the array footprint. We found that the USSE site could maintain a reseeded native plant community even a decade post‐restoration and that the array better supported native plant community persistence, with higher community‐level biomass, leaf nitrogen, and water content during extreme drought relative to the reference area. However, these responses were not observed following extreme rainfall, when plant productivity diminished across the site. During an average rainfall year, areas within the array were less diverse and conferred fewer ecosystem functions, yet these areas maintained more functions and greater diversity under extreme drought and comparable to greater productivity than the reference across the whiplash weather period. These findings underscore the potential of dryland USSE sites to confer plant community resistance to drought than areas outside of the array footprint, but with the caveat that this benefit may be reduced during higher rainfall periods.